actionbook/rust-call-graph

Rust Call Graph

Visualize function call relationships using LSP call hierarchy.

Usage

/rust-call-graph <function_name> [--depth N] [--direction in|out|both]

Options:

• --depth N: How many levels to traverse (default: 3)
• --direction: in (callers), out (callees), both

Examples:

• /rust-call-graph process_request - Show both callers and callees
• /rust-call-graph handle_error --direction in - Show only callers
• /rust-call-graph main --direction out --depth 5 - Deep callee analysis

LSP Operations

1. Prepare Call Hierarchy

Get the call hierarchy item for a function.

LSP(
  operation: "prepareCallHierarchy",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

2. Incoming Calls (Who calls this?)

LSP(
  operation: "incomingCalls",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

3. Outgoing Calls (What does this call?)

LSP(
  operation: "outgoingCalls",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

Workflow

User: "Show call graph for process_request"
    │
    ▼
[1] Find function location
    LSP(workspaceSymbol) or Grep
    │
    ▼
[2] Prepare call hierarchy
    LSP(prepareCallHierarchy)
    │
    ▼
[3] Get incoming calls (callers)
    LSP(incomingCalls)
    │
    ▼
[4] Get outgoing calls (callees)
    LSP(outgoingCalls)
    │
    ▼
[5] Recursively expand to depth N
    │
    ▼
[6] Generate ASCII visualization

Output Format

Incoming Calls (Who calls this?)

## Callers of `process_request`

main
└── run_server
    └── handle_connection
        └── process_request  ◄── YOU ARE HERE

Outgoing Calls (What does this call?)

## Callees of `process_request`

process_request  ◄── YOU ARE HERE
├── parse_headers
│   └── validate_header
├── authenticate
│   ├── check_token
│   └── load_user
├── execute_handler
│   └── [dynamic dispatch]
└── send_response
    └── serialize_body

Bidirectional (Both)

## Call Graph for `process_request`

                    ┌─────────────────┐
                    │      main       │
                    └────────┬────────┘
                             │
                    ┌────────▼────────┐
                    │   run_server    │
                    └────────┬────────┘
                             │
                    ┌────────▼────────┐
                    │handle_connection│
                    └────────┬────────┘
                             │
        ┌────────────────────┼────────────────────┐
        │                    │                    │
┌───────▼───────┐   ┌───────▼───────┐   ┌───────▼───────┐
│ parse_headers │   │ authenticate  │   │send_response  │
└───────────────┘   └───────┬───────┘   └───────────────┘
                            │
                    ┌───────┴───────┐
                    │               │
             ┌──────▼──────┐ ┌──────▼──────┐
             │ check_token │ │  load_user  │
             └─────────────┘ └─────────────┘

Analysis Insights

After generating the call graph, provide insights:

## Analysis

**Entry Points:** main, test_process_request
**Leaf Functions:** validate_header, serialize_body
**Hot Path:** main → run_server → handle_connection → process_request
**Complexity:** 12 functions, 3 levels deep

**Potential Issues:**
- `authenticate` has high fan-out (4 callees)
- `process_request` is called from 3 places (consider if this is intentional)

Common Patterns

| User Says | Direction | Use Case | |-----------|-----------|----------| | "Who calls X?" | incoming | Impact analysis | | "What does X call?" | outgoing | Understanding implementation | | "Show call graph" | both | Full picture | | "Trace from main to X" | outgoing | Execution path |

Visualization Options

| Style | Best For | |-------|----------| | Tree (default) | Simple hierarchies | | Box diagram | Complex relationships | | Flat list | Many connections | | Mermaid | Export to docs |

Mermaid Export

graph TD
    main --> run_server
    run_server --> handle_connection
    handle_connection --> process_request
    process_request --> parse_headers
    process_request --> authenticate
    process_request --> send_response

Related Skills

| When | See | |------|-----| | Find definition | rust-code-navigator | | Project structure | rust-symbol-analyzer | | Trait implementations | rust-trait-explorer | | Safe refactoring | rust-refactor-helper |